Electromagnetic and strong contributions to dAu soft coherent inelastic diffraction at RHIC

Charge separation relative to the reaction plane in Pb-Pb collisions at ffiffiffiffiffiffiffiffiffis NN p ¼2:76TeVB.Abelev et al.*(ALICE Collaboration)(Received 5July 2012;published 2January 2013)Measurements of charge-dependent azimuthal correlations with the ALICE detector at the LHC arereported for Pb-Pb collisions at ffiffiffiffiffiffiffiffis NN p ¼2:76TeV .Two-and three-particle charge-dependent azimuthal correlations in the pseudorapidity range j j <0:8are presented as a function of the collision centrality,particle separation in pseudorapidity,and transverse momentum.A clear signal compatible with a charge-dependent separation relative to the reaction plane is observed,which shows little or no collision energy dependence when compared to measurements at RHIC energies.This provides a new insight for under-standing the nature of the charge-dependent azimuthal correlations observed at RHIC and LHC energies.DOI:10.1103/PhysRevLett.110.012301PACS numbers:25.75.Ld,11.30.Er,11.30.Qc,12.38.AwThe possibility to observe parity violation in the strong interaction using relativistic heavy-ion collisions has been discussed for many years [1–3].In quantum chromody-namics (QCD),this symmetry violation originates in the interaction between quarks and topologically nontrivial gluonic fields,instantons,and sphalerons [4].This interac-tion,which is characterized by the topological charge [5],breaks the balance between the number of quarks with different chirality,resulting in a violation of the P and CP symmetry.In [6,7],it was suggested that in the vicinity of the deconfinement phase transition,and under the influ-ence of the strong magnetic field generated by the colliding nuclei,the quark spin alignment along the direction of the angular momentum (i.e.the direction of the magnetic field)and the imbalance of the left-and right-handed quarks,generates an electromagnetic current.The experimental search of these effects has intensified recently,following the realization that the consequent quark fragmentation into charged hadrons results in a charge separation along the direction of the magnetic field,and perpendicular to the reaction plane (the plane of symmetry of a collision defined by the impact parameter vector and the beam direction).This phenomenon is called the chiral magnetic effect (CME).Because of fluctuations in the sign of the topologi-cal charge,the resulting charge separation averaged over many collisions is zero.This makes the observation of the CME possible only via P -even observables,expressed in terms of two-particle and multiparticle correlations.The previous measurement of charge separation by the STAR Collaboration [8]is consistent with the qualitative expec-tations for the CME and has triggered an intense discussion [9–13].A significant source of uncertainty in the theoretical consideration of the CME is related to the expected center-of-mass energy dependence.In [7],the authors argued that the uncertainty in making any quantitative prediction relies on the time integration over which the magnetic field develops and decays.As long as a decon-fined state of matter is formed in a heavy-ion collision,the magnitude of the effect should either not change or should decrease with increasing energy [7].In addition,in [12]it is also suggested that there should be no energy depen-dence between the top RHIC and the LHC energies,based on arguments related to the universality of the underlying physical process,without however explicitly quantifying what the contribution of the different values and time evolution of the magnetic field for different energies will be.On the other hand,in [13]it is argued that the CME should strongly decrease at higher energies,because the magnetic field decays more rapidly.Such spread in the theoretical expectations makes it important to measure the charge-dependent azimuthal correlations at the LHC,where the collision energy is an order of magnitude higher compared to the RHIC.In this Letter we report the measurement of charge-dependent azimuthal correlations at midrapidity in Pb-Pb collisions at the center-of-mass energy per nucleon pair ffiffiffiffiffiffiffiffis NN p ¼2:76TeV by the ALICE Collaboration at the LHC.Azimuthal correlations among particles produced in a heavy-ion collision provide a powerful tool for the experi-mental study of particle production with respect to the reaction plane.They are usually quantified by the aniso-tropic flow coefficients,v n ,in a Fourier decomposition [14].Local violation of parity symmetry may result in the additional P -odd sinus terms [3,8,15]:dNd’ $1þ2X n ½v n; cos ðn Á’ Þþa n; sin ðn Á’ Þ ;(1)where Á’ ¼’ ÀÉRP is the azimuthal angle ’ of the charged particle of type relative to the reaction plane*Full author list given at the end of the article.Published by the American Physical Society under the terms of the Creative Commons Attribution 3.0License .Further distri-bution of this work must maintain attribution to the author(s)and the published article’s title,journal citation,and DOI.angle,ÉRP.The leading order coefficient a1; reflects the magnitude while the higher orders(a n; for n>1)describe the specific shape in azimuth of the effects from local parity violation.We thus employ a multiparticle correlator [15]that probes the magnitude of the a1coefficient,and at the same time suppresses the background correlations unrelated to the reaction plane:h cosð’ þ’ À2ÉRPÞi¼h cosÁ’ cosÁ’ iÀh sinÁ’ sinÁ’ i:(2) The indices and refer to the charge of the particles.The brackets denote an average over the particle pairs within the event as well as an average over the analyzed events.In practice,the reaction plane angle is not known and is esti-mated by constructing the event plane using azimuthal par-ticle distributions.In Eq.(2),the terms h cosÁ’ cosÁ’ i and h sinÁ’ sinÁ’ i quantify the correlations in-and out-of plane,respectively.The latter is sensitive to the charge correlations resulting from the CME:h sinÁ’ sinÁ’ i$ h a1; a1; i.The construction of the correlator in Eq.(2)as the difference between these two contributions suppresses correlations not related to the reaction plane orientation (nonflow).The contribution from the CME to the correla-tions of pairs of particles with same and opposite charge is expected to be similar in magnitude and opposite in sign. This expectation could be further modified by the medium created in a heavy-ion collision,that may result in the dilution of the correlations between particles with opposite sign[6,7].In order to evaluate each of the two terms in Eq.(2),we also measure the two-particle correlator:h cosð’ À’ Þi¼h cosÁ’ cosÁ’ iþh sinÁ’ sinÁ’ i;(3) which in contrast to the correlator in Eq.(2)is independent of the reaction plane angle and susceptible to the large P-even background contributions.The combination of these correlators provides access to both components, h cosÁ’ cosÁ’ i and h sinÁ’ cosÁ’ i,which is impor-tant for detailed comparisons with model calculations.It should be pointed out that both correlators of Eq.(2) and Eq.(3)could be affected by background sources.In [10],it is argued that the effect of momentum conservation influences in a similar way the pairs of particles with opposite and same charge,and could result in a potentially significant correction to both h cosð’ þ’ À2ÉRPÞi and h cosð’ À’ Þi.Also in[10],it was suggested that local charge conservation effects may be responsible for a sig-nificant part of the observed charge dependence of the correlator h cosð’ þ’ À2ÉRPÞi.Recent calculations [16]suggest that the correlator in Eq.(2)may have a negative(i.e.out-of-plane),charge-independent,dipole flow contribution originating fromfluctuations in the initial energy density of a heavy-ion collision.A description of the ALICE detector and its perform-ance can be found in[17,18].For this analysis,the follow-ing detector subsystems were used:the time projection chamber(TPC)[19],the silicon pixel detector(SPD), two forward scintillator arrays(VZERO),and two zero degree calorimeters(ZDC)[17].We analyzed a sample of about13Â106minimum-bias trigger events of Pb-Pb collisions atffiffiffiffiffiffiffiffis NNp¼2:76TeV collected with the ALICE detector.The standard ALICE offline event selection criteria[20]were applied,including a collision vertex cut ofÆ7cm along the beam axis.The collision centrality is estimated from the amplitude mea-sured by the VZERO detectors[17].The data sample is divided into centrality classes which span0%-70%of the hadronic interaction cross section,with the0%-5%class corresponding to the most central(i.e.smaller impact pa-rameter)collisions.Charged particles reconstructed by the TPC are accepted for analysis within j j<0:8and0:2< p T<5:0GeV=c.A set of requirements described in[20] were applied in order to ensure the quality of the tracks but also to reduce the contamination from secondary particles. To evaluate the systematic uncertainties in the analysis, events recorded with two different magneticfield polarities were analyzed leading to an uncertainty that is less than7% for all centrality classes.The cut on the collision vertex was varied fromÆ7cm toÆ10cm from the nominal collision point,with steps of1cm,contributing a maximum of5%to the total uncertainty.A bias due to the centrality determina-tion was studied by using multiplicities measured by the TPC or the SPD,rather than the VZERO,and was found to be less than10%.Contamination due to secondary tracks that do not originate from the collision vertex was reduced by requiring that the distance of closest approach between tracks and the primary vertex is less than2cm.The effect of secondary tracks on the measurement was estimated by varying the cut from2to4cm in steps of0.5cm and was calculated to be below15%.Effects due to nonuniform acceptance of the TPC were estimated to be below2%and are corrected for in the analysis.A significant contribution to the systematic error is coming from the uncertainty in the v2measurement,which is used as an estimate of the reaction plane resolution.The v2 estimate is obtained from the2-and4-particle cumulant analyses[20],which are affected in different ways by non-flow effects andflowfluctuations.For this analysis,v2was taken as the average of the two values,with half of the difference between v2f2g and v2f4g being attributed as the systematic uncertainty.The values of this uncertainty range from9%for the20%–30%centrality to18%(24%)for the 50%–60%(60%–70%)centrality class.The differences in the results from the four independent analysis methods (described below)were also considered as part of the system-atic uncertainty and were estimated to be3%for the 20%–30%and the50%–60%centrality bins and47%for the most peripheral centrality class.The contributions from all effects were added in quadrature to calculate the totalsystematic uncertainty.For the correlation between pairs of particles with the same charge it varies from 19%(28%)for the 20%–30%(50%–60%)centrality up to 55%for the 60%–70%centrality class.The correlations between oppo-site charged particles for 0%–60%centrality and for the same charge pairs for 0%–20%centrality are compatible with zero with a systematic error below 5:5Â10À5.Figure 1(a)presents the centrality dependence of the three-particle correlator,defined in Eq.(2).The correla-tions of the same charge pairs for the positive-positive and negative-negative combinations are found to be consistent within statistical uncertainties and are combined into one set of points,labeled same .The difference between the correlations of pairs with same and opposite charge indi-cates a charge dependence with respect to the reaction plane,as may be expected for the CME.To test the bias from the reaction plane reconstruction,four independent analyses were performed.The first analysis uses a cumu-lant technique [21],whereas for the three other analyses the orientation of the collision symmetry plane is estimated from the azimuthal distribution of charged particles in the TPC,and hits in the forward VZERO and ZDC detectors [22].There is a very good agreement between the results obtained with the event plane estimated from different detectors covering a wide range in pseudorapidity.This allows us to conclude that background sources due to corre-lations not related to the orientation of the reaction plane are negligible,with perhaps the exception of the peripheral collisions for the pairs of particles with opposite charge.Figure 1(b)shows the centrality dependence of the two-particle correlator h cos ð’ À’ Þi ,as defined in Eq.(3),which helps to constrain experimentally the P -even back-ground correlations.The statistical uncertainty is smaller than the symbol size.The two-particle correlations for the same and opposite charge combinations are always posi-tive and exhibit qualitatively similar centrality depen-dence,while the magnitude of the correlation is smaller for the same charged pairs.Our two-particle correlation results differ from those reported by the STARCollaboration for Au-Au collisions at ffiffiffiffiffiffiffiffis NN p ¼200GeV [8]for which negative correlations are observed for the same charged pairs.Figure 1(c)shows the h cosÁ’ cosÁ’ i and h sinÁ’ sinÁ’ i terms separately.For pairs of particles of the same charge,we observe that the h sinÁ’ sinÁ’ i correlations are larger than the h cosÁ’ cosÁ’ i ones.On the other hand,for pairs of opposite charge,the two terms are very close except for the most peripheral collisions.Further interpretation of the results presented in Fig.1(c)in terms of in-and out-of-plane correlations is complicated due to the significant nonflow contribution in h cos ð’ À’ Þi .Figure 2presents the three-particle correlator h cos ð’ þ’ À2ÉRP Þi as a function of the collision centrality com-pared to model calculations and results for RHIC energies.The statistical uncertainties are represented by the errorbars.The shaded area around the points indicates the systematic uncertainty based on the different sources described above.Also shown in Fig.2are STAR results [8].The small difference between the LHC and the RHIC data indicates little or no energy dependence for the three-particle correlator when changing from the collisionenergy of ffiffiffiffiffiffiffiffis NN p ¼0:2TeV to 2.76TeV .In Fig.2,the ALICE data are compared to the expectations from the HIJING model [23].The HIJING results for the three-particle correlations are divided by the experimentally〉)R P Ψ - 2βϕ + αϕ c o s (〈-0.50.5-3〉)βϕ-αϕ c o s (〈00.0020.0040.006centrality, %0.0020.003FIG.1(color online).(a)Centrality dependence of the correla-tor defined in Eq.(2)measured with the cumulant method and from correlations with the reaction plane estimated using the TPC,the ZDC,and the VZERO detectors.Only statistical errors are shown.The points are displaced slightly in the horizontal direction for visibility.(b)Centrality dependence of the two-particle corre-lator defined in Eq.(3)compared to the STAR data [8].The width of the solid red lines indicates the systematic uncertainty of the ALICE measurement.(c)Decomposition of the correlators into h cosÁ’ cosÁ’ i and h sinÁ’ sinÁ’ i terms.The ALICE results in (b)and (c)are obtained with the cumulant method.measured value of v 2(i.e.h cos ð’ þ’ À2’c Þi =v 2f 2g )as reported in [20]due to the absence of collective azimuthal anisotropy in this model.Since the points do not exhibit any significant difference between the correlations of pairs with same and opposite charge,they were averaged in the figure.The correlations from HIJING show a significant increase in the magnitude for very peripheral collisions.This can be attributed to correlations not related to the reaction plane orientation,in particular,from jets [8].The results from ALICE in Fig.2show a strong corre-lation for pairs with the same charge and simultaneously a very weak correlation for the pairs of opposite charge.This difference in the correlation magnitude depending on the charge combination could be interpreted as ‘‘quenching’’of the charge correlations for the case when one of the particles is emitted toward the center of the dense medium created in a heavy-ion collision [6,7].An alternative ex-planation can be provided by a recent suggestion [16]that the value of the charge-independent version of the corre-lator defined in Eq.(2)is dominated by directed flow fluctuations.The sign and the magnitude of these fluctua-tions based on a hydrodynamical model calculation for RHIC energies [16]appear to be very close to the mea-surement.Our results for charge-independent correlations are given by the shaded band in Fig.2.The thick solid line in Fig.2shows a prediction [13]for the same sign correlations due to the CME at LHC ener-gies.The model makes no prediction for the absolute magnitude of the effect and can only describe the energy dependence by taking into account the duration and time evolution of the magnetic field.It predicts a decrease of correlations by about a factor of 5from RHIC to LHC,which would significantly underestimate the observed magnitude of the same sign correlations seen at the LHC.At the same time in [7,12],it was suggested that the CME might have the same magnitude at the LHC and at RHIC energies.Figure 3shows the dependence of the three-particle correlator on the transverse momentum difference,j p T ; Àp T ; j ,the average transverse momentum,ðp T ; þp T ; Þ=2,and the pseudorapidity separation,j À j ,of the pair for the 30%-40%centrality range.The pairs of opposite charge do not show any significant dependence on the pseudorapidity difference,while there is a dependencecentrality, %〉)R P Ψ - 2βϕ + αϕ c o s (〈-0.6-0.4-0.200.20.40.6-3FIG.2(color online).The centrality dependence of the three-particle correlator defined in Eq.(2).The circles indicate the ALICE results obtained from the cumulant analysis.The stars show the STAR data from [8].The triangles represent the three-particle correlations [h cos ð’ þ’ À2’c Þi ]from HIJING [23]corrected for the experimentally measured v 2f 2g [20].Points are displaced horizontally for visibility.A model prediction for the same sign correlations incorporating the chiral magnetic effect for LHC energies [13]is shown by the solid line.The shaded band represents the centrality dependence of the charge-independent correlations.)| (GeV/c T,β - p T,α|p 〉)R P Ψ - 2βϕ + αϕc o s (〈-0.4-0.20.2-3))/2 (GeV/c T,β + p T,α(p |βη - αη = |η∆FIG.3(color online).The three-particle correlator defined in Eq.(2)as a function of (a)the transverse momentum difference,j p T ; Àp T ; j ,(b)the average transverse momentum,ðp T ; þp T ; Þ=2,and (c)the rapidity separation,j À j ,of the charged particle pair of same (closed symbols)and opposite (open symbols)sign.on j p T ; Àp T ; j (stronger)and ðp T ; þp T ; Þ=2(weaker).The correlations for pairs of particles of the same charge show no strong dependence on the p T difference,allowing one to exclude any type of short range correlations (e.g.quantum statistics correlations)as the main source of the effect.In addition,it is seen that the magnitude of the same charge correlations increases with increasing average p T of the pair.This observation is in contradiction to the initial expectations from theory [7]that the effect should originate from low p T particles.The dependence of the correlations on the j À j indicates a width of one unit in pseudor-apidity,beyond which the value of h cos ð’ þ’ À2ÉRP Þi is close to zero up to Á %1:5.Similar results were reported also at RHIC energies [8].At the moment there are no quantitative model calculations of the charge-dependent differential correlations.In summary,we have measured the charge-dependentazimuthal correlations in Pb-Pb collisions at ffiffiffiffiffiffiffiffis NN p ¼2:76TeV at the LHC using the ALICE detector.Both two-and three-particle correlations are reported.A clear signal compatible with a charge-dependent separation rela-tive to the reaction plane is observed.However,our results are not described by the only available quantitative model prediction of the CME for the LHC energy.The lack of realistic model calculations for the centrality and pair differential dependencies based on models incorporating CME and possible background contributions does not allow us to make a firm conclusion regarding the nature of the charge-dependent correlations originally observed at RHIC and now established at the LHC.The observation of a small collision energy dependence of the three-particle correlation and the simultaneous significant change in the two-particle correlations between top RHIC and LHC energies put stringent constraints on models built to interpret such correlations.Analyses of higher harmonic correlations are planned and may yield a better understanding of the com-plex charge-dependent correlations 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Roman,74G.Cara Romeo,17W.Carena,6F.Carena,6N.Carlin Filho,75F.Carminati,6A.Casanova Dı´az,54J.Castillo Castellanos,40J.F.Castillo Hernandez,26E.A.R.Casula,76V.Catanescu,25 C.Cavicchioli,6C.Ceballos Sanchez,77J.Cepila,2P.Cerello,16B.Chang,37,78S.Chapeland,6J.L.Charvet,40S.Chattopadhyay,10S.Chattopadhyay,64I.Chawla,5M.Cherney,79C.Cheshkov,6,80B.Cheynis,80V.Chibante Barroso,6D.D.Chinellato,81P.Chochula,6M.Chojnacki,57S.Choudhury,10P.Christakoglou,56 C.H.Christensen,47P.Christiansen,82T.Chujo,53S.U.Chung,83C.Cicalo,84L.Cifarelli,8,6,18F.Cindolo,17J.Cleymans,70F.Coccetti,18F.Colamaria,22D.Colella,22G.Conesa Balbastre,34Z.Conesa del Valle,6 P.Constantin,27G.Contin,73J.G.Contreras,74T.M.Cormier,63Y.Corrales Morales,50P.Cortese,85I.Corte´s Maldonado,86M.R.Cosentino,66F.Costa,6M.E.Cotallo,58E.Crescio,74P.Crochet,39E.Cruz Alaniz,9E.Cuautle,87L.Cunqueiro,54A.Dainese,55,31H.H.Dalsgaard,47A.Danu,88D.Das,64K.Das,64I.Das,65S.Dash,89A.Dash,81S.De,10G.O.V.de Barros,75A.De Caro,90,18G.de Cataldo,91J.de Cuveland,21A.De Falco,76D.De Gruttola,90H.Delagrange,32A.Deloff,92V.Demanov,69N.De Marco,16E.De´nes,7 S.De Pasquale,90A.Deppman,75G.D.Erasmo,22R.de Rooij,57M.A.Diaz Corchero,58D.Di Bari,22T.Dietel,28C.Di Giglio,22S.Di Liberto,93A.Di Mauro,6P.Di Nezza,54R.Divia`,6Ø.Djuvsland,23A.Dobrin,63,82T.Dobrowolski,92I.Domı´nguez,87B.Do¨nigus,26O.Dordic,94O.Driga,32A.K.Dubey,10A.Dubla,57L.Ducroux,80P.Dupieux,39M.R.Dutta Majumdar,10A.K.Dutta Majumdar,64D.Elia,91D.Emschermann,28。

电坏处英语作文The Disadvantages of Electronics。

In today's modern world, electronics have become an integral part of our daily lives. From smartphones to laptops to televisions, we are constantly surrounded by electronic devices. While these devices have undoubtedly made our lives more convenient, they also come with their fair share of disadvantages.One of the biggest drawbacks of electronics is their negative impact on our health. The blue light emitted by screens can disrupt our sleep patterns and cause eye strain. Prolonged use of electronic devices has also been linked to an increased risk of obesity, as it often leads to a sedentary lifestyle. Additionally, the constant exposure to electromagnetic radiation from electronic devices hasraised concerns about its potential long-term effects onour health.Another disadvantage of electronics is their contribution to environmental pollution. Electronic devices contain hazardous materials such as lead, mercury, and cadmium, which can leach into the soil and water when improperly disposed of. The manufacturing process of electronics also generates a significant amount of electronic waste, further adding to the environmental burden.Furthermore, the widespread use of electronics has led to a decline in face-to-face communication. Many people now prefer to communicate through text messages and social media, rather than having meaningful conversations in person. This has resulted in a lack of interpersonal skills and has made it difficult for people to form genuine connections with others.In addition, the constant need to upgrade to the latest electronic devices has led to a culture of consumerism and materialism. People are often pressured to keep up with the latest trends, leading to unnecessary spending and a disregard for the environmental impact of constantlydiscarding old devices.Moreover, the overreliance on electronic devices has made us more vulnerable to cyber threats. Hacking, identity theft, and online scams have become increasingly common, putting our personal and financial information at risk.In conclusion, while electronics have undoubtedly revolutionized the way we live, it is important to recognize and address their disadvantages. From their impact on our health and the environment to their influence on our social interactions and consumer behavior, it is crucial to find a balance between the benefits and drawbacks of electronic devices. By being mindful of these disadvantages, we can work towards using electronics in a more responsible and sustainable manner.。

Title: The Legacy of James Clerk MaxwellJames Clerk Maxwell, a brilliant scientist of the 19th century, revolutionized our understanding of electromagnetism and paved the way for future technological advancements. Born in Scotland, Maxwell's curiosity and dedication to scientific inquiry led him to groundbreaking discoveries that are still relevant today.Maxwell's most significant contribution was his theory of electromagnetism, which unified the previously separate fields of electricity and magnetism. His mathematical equations, known as Maxwell's equations, described the behavior of electromagnetic fields with precision and elegance. These equations are the foundation of modern electronics, telecommunications, and even relativity theory.Moreover, Maxwell's prediction of electromagnetic waves was a pivotal moment in the history of science. His calculations suggested that these waves, traveling through space at the speed of light, could exist. This prediction not only explained the phenomenon of light but also foretold the existence of radio waves, which later became the basis of wireless communication.Beyond his scientific achievements, Maxwell's legacy lies in his approach to research. He was a meticulous experimentalist, always striving to verify his theoretical predictions through rigorous experiments. His dedication to the scientific method and his commitment to precision set an example for future generations of scientists.In conclusion, James Clerk Maxwell's contributions to science are immeasurable. His theory of electromagnetism and prediction of electromagnetic waves have transformed our world, laying the foundation for modern technology. His legacy remains alive in the scientific community, inspiring us to continue exploring the wonders of the natural world.。

a rXiv:n ucl-t h /441v28Ma y2The decay ρ0→π++π−+γand the coupling constant g ρσγA.Gokalp ∗and O.Yilmaz †Physics Department,Middle East Technical University,06531Ankara,Turkey(February 8,2008)Abstract The experimental branching ratio for the radiative decay ρ0→π++π−+γis used to estimate the coupling constant g ρσγfor a set of values of σ-meson parameters M σand Γσ.Our results are quite different than the values of this constant used in the literature.PACS numbers:12.20.Ds,13.40.HqTypeset using REVT E XThe radiative decay processρ0→π++π−+γhas been studied employing different approaches[1,5].There are two mechanisms that can contribute to this radiative decay: thefirst one is the internal bremsstrahlung where one of the charged pions from the decay ρ0→π++π−emits a photon,and the second one is the structural radiation which is caused by the internal transformation of theρ-meson quark structure.Since the bremsstrahlung is well described by quantum electrodynamics,different methods have been used to estimate the contribution of the structural radiation.Singer[1]calculated the amplitude for this decay by considering only the bremsstrahlung mechanism since the decayρ0→π++π−is the main decay mode ofρ0-meson.He also used the universality of the coupling of theρ-meson to pions and nucleons to determine the coupling constant gρππfrom the knowledge of the coupling constant gρter,Renard [3]studied this decay among other vector meson decays into2π+γfinal states in a gauge invariant way with current algebra,hard-pion and Ward-identities techniques.He,moreover, established the correspondence between these current algebra results and the structure of the amplitude calculated in the single particle approximation for the intermediate states.In corresponding Feynman diagrams the structural radiation proceeds through the intermediate states asρ0→S+γwhere the meson S subsequently decays into aπ+π−pair.He concluded that the leading term is the pion bremsstrahlung and that the largest contribution to the structural radiation amplitude results from the scalarσ-meson intermediate state.He used the rough estimate gρσγ≃1for the coupling constant gρσγwhich was obtained with the spin independence assumption in the quark model.The coupling constant gρππwas determined using the then available experimental decay rate ofρ-meson and also current algebra results as3.2≤gρππ≤4.9.On the other hand,the coupling constant gσππwas deduced from the assumed decay rateΓ≃100MeV for theσ-meson as gσππ=3.4with Mσ=400MeV. Furthermore,he observed that theσ-contribution modifies the shape of the photon spectrum for high momenta differently depending on the mass of theσ-meson.We like to note, however,that the nature of theσ-meson as a¯q q state in the naive quark model and therefore the estimation of the coupling constant gρσγin the quark model have been a subject ofcontroversy.Indeed,Jaffe[6,7]lately argued within the framework of lattice QCD calculation of pseudoscalar meson scattering amplitudes that the light scalar mesons are¯q2q2states rather than¯q q states.Recently,on the other hand,the coupling constant gρσγhas become an important input for the studies ofρ0-meson photoproduction on nucleons.The presently available data[8] on the photoproduction ofρ0-meson on proton targets near threshold can be described at low momentum transfers by a simple one-meson exchange model[9].Friman and Soyeur [9]showed that in this picture theρ0-meson photoproduction cross section on protons is given mainly byσ-exchange.They calculated theγσρ-vertex assuming Vector Dominance of the electromagnetic current,and their result when derived using an effective Lagrangian for theγσρ-vertex gives the value gρσγ≃2.71for this coupling ter,Titov et al.[10]in their study of the structure of theφ-meson photoproduction amplitude based on one-meson exchange and Pomeron-exchange mechanisms used the coupling constant gφσγwhich they calculated from the above value of gρσγinvoking unitary symmetry arguments as gφσγ≃0.047.They concluded that the data at low energies near threshold can accommodate either the second Pomeron or the scalar mesons exchange,and the differences between these competing mechanisms have profound effects on the cross sections and the polarization observables.It,therefore,appears of much interest to study the coupling constant gρσγthat plays an important role in scalar meson exchange mechanism from a different perspective other than Vector Meson Dominance as well.For this purpose we calculate the branching ratio for the radiative decayρ0→π++π−+γ,and using the experimental value0.0099±0.0016for this branching ratio[11],we estimate the coupling constant gρσγ.Our calculation is based on the Feynman diagrams shown in Fig.1.Thefirst two terms in thisfigure are not gauge invariant and they are supplemented by the direct term shown in Fig.1(c)to establish gauge invariance.Guided by Renard’s[3]current algebra results,we assume that the structural radiation amplitude is dominated byσ-meson intermediate state which is depicted in Fig. 1(d).We describe theρσγ-vertex by the effective LagrangianL int.ρσγ=e4πMρMρ)2 3/2.(3)The experimental value of the widthΓ=151MeV[11]then yields the value g2ρππ2gσππMσ π· πσ.(4) The decay width of theσ-meson that follows from this effective Lagrangian is given asΓσ≡Γ(σ→ππ)=g2σππ8 1−(2Mπ2iΓσ,whereΓσisgiven by Eq.(5).Since the experimental candidate forσ-meson f0(400-1200)has a width (600-1000)MeV[11],we obtain a set of values for the coupling constant gρσγby considering the ranges Mσ=400-1200MeV,Γσ=600-1000MeV for the parameters of theσ-meson.In terms of the invariant amplitude M(Eγ,E1),the differential decay probability for an unpolarizedρ0-meson at rest is given bydΓ(2π)31Γ= Eγ,max.Eγ,min.dEγ E1,max.E1,min.dE1dΓ[−2E2γMρ+3EγM2ρ−M3ρ2(2EγMρ−M2ρ)±Eγfunction ofβin Fig.5.This ratio is defined byΓβRβ=,Γtot.= Eγ,max.50dEγdΓdEγ≃constant.(10)ΓσM3σFurthermore,the values of the coupling constant gρσγresulting from our estimation are in general quite different than the values of this constant usually adopted for the one-meson exchange mechanism calculations existing in the literature.For example,Titov et al.[10] uses the value gρσγ=2.71which they obtain from Friman and Soyeur’s[9]analysis ofρ-meson photoproduction using Vector Meson Dominance.It is interesting to note that in their study of pion dynamics in Quantum Hadrodynamics II,which is a renormalizable model constructed using local gauge invariance based on SU(2)group,that has the sameLagrangian densities for the vertices we use,Serot and Walecka[14]come to the conclusion that in order to be consistent with the experimental result that s-waveπN-scattering length is anomalously small,in their tree-level calculation they have to choose gσππ=12.Since they use Mσ=520MeV this impliesΓσ≃1700MeV.If we use these values in our analysis,we then obtain gρσγ=11.91.Soyeur[12],on the other hand,uses quite arbitrarly the values Mσ=500 MeV,Γσ=250MeV,which in our calculation results in the coupling constant gρσγ=6.08.We like to note,however,that these values forσ-meson parameters are not consistent with the experimental data onσ-meson[11].Our analysis and estimation of the coupling constant gρσγusing the experimental value of the branching ratio of the radiative decayρ0→π++π−+γgive quite different values for this coupling constant than used in the literature.Furthermore,since we obtain this coupling constant as a function ofσ-meson parameters,it will be of interest to study the dependence of the observables of the reactions,such as for example the photoproduction of vector mesons on nucleonsγ+N→N+V where V is the neutral vector meson, analyzed using one-meson exchange mechanism on these parameters.AcknowledgmentsWe thank Prof.Dr.M.P.Rekalo for suggesting this problem to us and for his guidance during the course of our work.We also wish to thank Prof.Dr.T.M.Aliev for helpful discussions.REFERENCES[1]P.Singer,Phys.Rev.130(1963)2441;161(1967)1694.[2]V.N.Baier and V.A.Khoze,Sov.Phys.JETP21(1965)1145.[3]S.M.Renard,Nuovo Cim.62A(1969)475.[4]K.Huber and H.Neufeld,Phys.Lett.B357(1995)221.[5]E.Marko,S.Hirenzaki,E.Oset and H.Toki,Phys.Lett.B470(1999)20.[6]R.L.Jaffe,hep-ph/0001123.[7]M.Alford and R.L.Jaffe,hep-lat/0001023.[8]Aachen-Berlin-Bonn-Hamburg-Heidelberg-Munchen Collaboration,Phys.Rev.175(1968)1669.[9]B.Friman and M.Soyeur,Nucl.Phys.A600(1996)477.[10]A.I.Titov,T.-S.H.Lee,H.Toki and O.Streltrova,Phys.Rev.C60(1999)035205.[11]Review of Particle Physics,Eur.Phys.J.C3(1998)1.[12]M.Soyeur,nucl-th/0003047.[13]S.I.Dolinsky,et al,Phys.Rep.202(1991)99.[14]B.D.Serot and J.D.Walecka,in Advances in Nuclear Physics,edited by J.W.Negeleand E.Vogt,Vol.16(1986).TABLESTABLE I.The calculated coupling constant gρσγfor differentσ-meson parametersΓσ(MeV)gρσγ500 6.97-6.00±1.58 8008.45±1.77600 6.16-6.68±1.85 80010.49±2.07800 5.18-9.11±2.64 90015.29±2.84900 4.85-10.65±3.14 90017.78±3.23Figure Captions:Figure1:Diagrams for the decayρ0→π++π−+γFigure2:The photon spectra for the decay width ofρ0→π++π−+γ.The contributions of different terms are indicated.Figure3:The pion energy spectra for the decay width ofρ0→π++π−+γ.The contri-butions of different terms are indicated.Figure4:The decay width ofρ0→π++π−+γas a function of minimum detected photon energy.Figure5:The ratio Rβ=Γβ。

LOGO第一章记叙文体的英译与写作第二章法律文体的英译与写作第三章应用文体英译与写作第四章广告文体英译与写作QQ:105448245424学时科技英语(二)EST ⅡREFERENCES:1、张梦井，杜耀文汉英科技翻译指南，航空工业出版社，19962、王运，实用科技英语翻译技巧，科技文献出版社，19923、熊第霖，英文科技写作，国防工业出版社，20011 记叙文体的汉译英1. 1 科技论文的汉译英问题1. 2 摘要的英译与写作1. 3 国际会议文献的英译与写作1. 1 科技论文的汉译英问题一、科技论文的分类◆按学科的性质和功能⏹基础学科论文⏹技术学科论文⏹应用学科论文◆按照写作目的和发挥的作用⏹学术性论文⏹技术性论文⏹学位论文◆按论文内容所属学科数学论文物理论文化学论文天文学论文机械工程技术论文建筑工程技术论文◆按研究和写作方法理论推导型实(试)验研究型观测型设计计算型发现发明型争鸣型综述型Title标题Abstract摘要Keywords关键词Table of contents目录Nomenclature术语表Introduction引言正文Acknowledgement致谢Reference参考文献Appendix附录Methods方法Results结果Discussion讨论Conclusion结论二、科技论文的一般结构LOGOacknowledgmentReferencesTitle 标题Author 作者Abstract 摘要Introduction 引言4 Summary and conclusion三、论文标题的英译与写作1、标题的作用⏹Generalizing the Text⏹Attracting the Reader⏹Facilitating the Retrieval2、标题的长度（单词总数）及词性⏹标题不宜过长，大多为12个单词以内。

⏹标题中用得最多的是名词（包括动名词），除名词外，用得较多的是介词，有时使用形容词、冠词、连词、副词。

Versions of this article appeared in Power Quality Magazine, Sep 1999 and PCIM Magazine Feb 2000 CURRENT-LIMITING FUSES IMPROVE POWER QUALITYbyR. WilkinsOverdee, Rocky Lane Heswall, Wirral, CH60 0BZ, UKH.C.ClineGould Shawmut, 374 Merrimac Street Newburyport, MA01950INTRODUCTIONVoltage sags (sometimes called voltage dips) in power networks due to power system short-circuit faults can cause serious problems for computer systems, adjustable-speed drives, and other industrial and domestic systems [1,2]. The cost of downtime and incorrect operation of equipment is becoming increasingly important. A recent study showed that major industrial users in South Africa suffer annual losses of more than $200 million due to voltage sags [3].The effect of a voltage sag is dependent upon its magnitude and duration. A curve published by the Information Technology Industry Council (ITIC, formerly known as CBEMA), is often used as a yardstick for the assessment of voltage sags. This curve, shown in Fig.1, defines overvoltage and undervoltage limits as a function of time. The region in between these two limits is a region of acceptable power quality. Although the ITIC (CBEMA) curve is strictly applicable only to 120V single-phase equipment subject to very specific types of voltage waves, it is nevertheless a useful general guide for other power systems.For a bolted fault to ground the faulted bus voltage will drop to zero. Fig.1 shows that for this case the duration of the fault must be less than 20ms to fall within the ITIC (CBEMA) limits. It follows that the operating speed of protection systems plays a key role in mitigating the effects of voltage sags and the improving of power quality [2,3,4]. The high-speed clearance provided by current-limiting fuses, which have no moving parts, can make a significant contribution to the improvement of power quality.OPERATION OF CURRENT-LIMITING FUSESCurrent-limiting fuses have been used for many years to provide high-speed protection of low-voltage and medium-voltage power systems. Fig.2 illustrates the construction of a typical modern current-limiting fuse. The fuse elements are typically made from silver or copper strip, and have reduced cross-sectional areas in a number of places. They are surrounded by compacted quartz sand in an insulating tube. When a short-circuit fault occurs, the reduced cross-sectional areas heat up and melt very quickly and form a number of electric arcs, which are then controlled and eventually quenched and extinguished by the surrounding sand. The appearance of the arcs corresponds electrically to the sudden switching of the fuse from a low-resistance state to a high-resistance state. This causes a rapid reduction in circuit current, limiting the peak current whichis permitted to flow in the circuit, and consequently limiting the “let-through I2t”. This is the integral of the square of the current over the fault period, and is a measure of the energy which must be absorbed by the circuit components. Fig.3 is a typical test oscillogram showing the breaking of a short-circuit fault current in an a.c. circuit. During the pre-arcing period the current closely follows the available current wave, the voltage drop across the fuse being low. However when arcing begins the fuse resistance and voltage increase rapidly, and the current is forced down to zero well before the natural zero of the prospective current wave.The peak system current is limited to a level well below the peak available current, dramatically reducing the heating and electromagnetic forces experienced by the power system components. REDUCTION OF VOLTAGE SAG DURATIONThe reduction of heating and electromagnetic stresses (both of which depend upon the square of the current) in power systems protected by current-limiting fuses is well known.However, it is not generally realized that current-limiting fuses make an important contribution to the improvement of power quality, because they also reduce the duration of voltage sags caused by short-circuit faults.As an example, consider the simple system shown in Fig.4. This represents a typical motor control center with 2 smaller motors (M1 and M2) and 2 larger motors (M3 and M4), protected by current-limiting fuses rated at 150% of the motor full-load current. For a fault at bus 6, (on the terminals of M4), bus 2 is the "point of common coupling", as far as the other parallel-connected motor loads are concerned [1].Fig.5 shows the effects on the voltage at bus 2 of a 3-phase short-circuit fault at bus 6, with M1 and M3 initially lightly loaded and M2 and M4 fully loaded. The fault is cleared by operation of the 3 fuses in line 5. These results were computed using the method described in [5], which uses a standard fuse model and takes into account 3-phase effects in the operation of the fuses as well as motor electrical and mechanical transients.When the fault occurs the voltage at the common bus 2 sags to a low level, but only for a few milliseconds, until the fuses melt. In the cases shown the melting times are 9.2,5.2 and 3.3ms, so the sag duration is well within the ITIC (CBEMA) limit shown in Fig.1. After the fuses switch to the arcing mode the bus voltage is raised due to the appearance of the fuse arc voltages, and the fault currents in the three phases are forced to zero. The highest peak current in line 5 is 13.7 p.u. It is necessary that the voltages produced by fuse operation are not so high as to be in the upper region of unacceptable power quality. The waveshape of the voltage transients produced during fuse operation is non-standard as far as the ITIC (CBEMA) curve is concerned, but if we approximate them as half-sine waves of medium frequency they correspond to r.m.s. values of 1.45, 1.53 and 1.34 per-unit with durations of 2.5, 3.4 and 1.34 milliseconds. These points are close to the upper ITIC (CBEMA) curve, but do not suggest any significant problem [1].The raising of the bus voltage during the fuse arcing phase aids the re-acceleration of the parallel-connected motors. During the fault the speed of the unfaulted motors does not drop significantly.If the fault had been at the terminals of one of the smaller motors, M1 or M2, clearance of the fault by the corresponding (smaller) fuses would be faster still, with even less disturbance to the system. The system data used here is typical of such systems. However, for very weak systems, with a very large supply impedance, the short-circuit current may be too low to cause fuse operation in less than one half-cycle [1].NON-CURRENT-LIMITING PROTECTIVE DEVICESDevices such as circuit-breakers or expulsion fuses have a different operating principle. The switching arc is extinguished at a current zero of the a.c. wave. This may take several a.c. cycles and during this period no significant current limitation occurs.Fig.6 shows the computed interruption transients for the example system if the current-limiting fuses are replaced by non-current-limiting devices which produce negligible arc voltage and which take about 2½ cycles to clear the fault. The high peak after the first quarter-cycle is composed of the fault current from the source via line 1 plus contributions from all the parallel-connected motors. There is no current limitation, which gives higher thermal and electromagnetic stresses on the circuit components. The peak network current is 21 p.u. while the I2t let through after the fault is cleared is almost 10 times higher than if the circuit were protected by the fuse.In this case the voltage at bus 2 sags to about 0.15-0.22 per-unit for 41-46 milliseconds, which is well in the lower region of unacceptable power quality shown in Fig.1. However bus 2 voltage remains depressed even after the fault has been cleared. It increases slowly from about 0.6 per-unit and remains below the ITIC (CBEMA) curve for a considerable time. The reason for this is that the speed of the parallel-connected motors drops significantly during the long-duration voltage sag. After the fault is removed the motors re-accelerate, drawing a high current from the supply, which causes the duration of the voltage sag at bus 2 to be further extended. This effect has also been noted in measurements on a utility network [4].Fig.7 shows how these results relate to the ITIC curve. For each data point an approximate r.m.s. value of voltage has been plotted for the corresponding time duration.CONCLUSIONCurrent-limiting fuses provide protection against disruptive heating and electromagnetic effects, but also make an important contribution to the improvement of power quality. They achieve this by operating within one half-cycle, to limit the duration of voltage sags, and without producing unacceptably high voltages. The resulting short duration of the disturbance to the system avoids further depression of voltages due to motor re-acceleration.Using fuses to improve the power quality of a power system is also a very inexpensive option.For systems where the cost of installing uninterruptible power supplies and similar types ofequipment cannot be justified, high-speed protection by current-limiting fuses is veryeconomical way of mitigating the effects of voltage sags.REFERENCES[1]M.H.J. Bollen. "Voltage sags : effects, mitigation and prediction" Power Engineering Journal , June 1996, pp 129-135. [2] R. Wilkins and M.H.J. Bollen. "The role of current-limiting fuses in power qualityimprovement" 3rd International Conference on Power Quality , Amsterdam, 24-27October 1994.[3] G. Topham. "Influence of the design and operation of protection and control on powerquality". Power Engineering Journal , December 1998, pp 253-258.[4] Lj.A Kojovic, S.P. Hassler, K.L. Leix, C.W. Williams and E.E. Baker. "Comparativeanalysis of expulsion and current-limiting fuse operation in distribution systems forimproved power quality and protection" IEEE Transactions on Power Delivery 1997.Paper PE-770-PWRD-0-06-1007.[5]R. Wilkins, A.J. McDonald and M. Castillo. "Computation of short-circuit transients inindustrial networks protected by current-limiting fuses". 8th International Symposium onShort-Circuit Currents in Power Systems , Brussels, 8-10 October 1998. 00.511.522.533.544.550.00010.0010.010.1110100duration , secp.u.voltage Fig.1 ITIC (CBEMA) curve.Fig.2 Construction of a typical current-limiting fuse.Fig. 4. Example system.Fig.5 Transients in system protected by current-limiting fuses.Fig.6 Transients in system protected by non-current-limiting devices. 0.5233.544.50.0001 0.001 0.01 0.1 1 10 100 duration , sec p.u. voltageFig.7 Voltage sags and peaks in relation to ITIC curve.Below is given annual work summary, do not need friends can download after editor deleted Welcome to visit againXXXX annual work summaryDear every leader, colleagues:Look back end of XXXX, XXXX years of work, have the joy of success in your work, have a collaboration with colleagues, working hard, also have disappointed when encountered difficulties and setbacks. Imperceptible in tense and orderly to be over a year, a year, under the loving care and guidance of the leadership of the company, under the support and help of colleagues, through their own efforts, various aspects have made certain progress, better to complete the job. For better work, sum up experience and lessons, will now work a brief summary.To continuously strengthen learning, improve their comprehensive quality. With good comprehensive quality is the precondition of completes the labor of duty and conditions. A year always put learning in the important position, trying to improve their comprehensive quality. Continuous learning professional skills, learn from surrounding colleagues with rich work experience, equip themselves with knowledge, the expanded aspect of knowledge, efforts to improve their comprehensive quality.The second Do best, strictly perform their responsibilities. Set up the company, to maximize the customer to the satisfaction of the company's products, do a good job in technical services and product promotion to the company. And collected on the properties of the products of the company, in order to make improvement in time, make the products better meet the using demand of the scene.Three to learn to be good at communication, coordinating assistance. On‐site technical service personnel should not only have strong professional technology, should also have good communication ability, a lot of a product due to improper operation to appear problem, but often not customers reflect the quality of no, so this time we need to find out the crux, and customer communication, standardized operation, to avoid customer's mistrust of the products and even the damage of the company's image. Some experiences in the past work, mentality is very important in the work, work to have passion, keep the smile of sunshine, can close the distance between people, easy to communicate with the customer. Do better in the daily work to communicate with customers and achieve customer satisfaction, excellent technical service every time, on behalf of the customer on our products much a understanding and trust.Fourth, we need to continue to learn professional knowledge, do practical grasp skilled operation. Over the past year, through continuous learning and fumble, studied the gas generation, collection and methods, gradually familiar with and master the company introduced the working principle, operation method of gas machine. With the help of the department leaders and colleagues, familiar with and master the launch of the division principle, debugging method of the control system, and to wuhan Chen Guchong garbage power plant of gas machine control system transformation, learn to debug, accumulated some experience. All in all, over the past year, did some work, have also made some achievements, but the results can only represent the past, there are some problems to work, can't meet the higher requirements. In the future work, I must develop the oneself advantage, lack of correct, foster strengths and circumvent weaknesses, for greater achievements. Looking forward to XXXX years of work, I'll be more efforts, constant progress in their jobs, make greater achievements. Every year I have progress, the growth of believe will get greater returns, I will my biggest contribution to the development of the company, believe inyourself do better next year!I wish you all work study progress in the year to come.。

电力词汇供电和用电波形质量Waveformquality电压和电流波形的正弦形程度。

城市供电Urbanpowersupply大面积停电Large-scaleconsumeroutage大型企业供电Powersupplyoflargeenterprise单边供电Singlesidefeeding单回路供电Single-circuitpowersupply单相供电Single-phasepowersupply地铁供电Powersupplytosubway地下供电Undergroundpowersupply电力牵引供电PowersupplyofelectrictractionEL力销售Electricitymarketing电力营销Electricitymarketing以满足人们的电力消费需求为目的的基本活动。

电能质量Electricpowerquality电压波动和变Voltagefluctuationandflicker一系列电压随机变动或工频电压包络线的周期性变化，以及由此引起的照明闪变。

it压和电流不平衡度Unsymmetryofvoltageandcurrent各相电压、电流幅值和相位的不对称程度。

电压质量Voltagequality动态电压恢复器Dynamicvoltagerecovery(DVR)能通过串联变压器向馈线注入可控幅值、相角和频率的电压，从而恢复负荷侧的电压质量。

独立电源Independentelectricsupply多回路供电Multiplefeed多相供电Polyphasepowersupply高层建筑物供电High-risebuildingpowersupply高压供电High-voltagepowersupply供电Powersupply供电点Power-supplypointDL/T一用户受电装置接入供电网中的位置。

供电电源Power-supplysource供电方案Schemeofpowersupply电力供应的具体实施计划。

北师大版教材高考英语第二轮复习书面表达专题之模块话题作文精选（必修一至选修八）假如你叫陈宇，你的英国笔友Mike在上次来信中谈到了低碳生活这个话题。

最近几个月校倡导学生过低碳生活、过节约生活、做有责任感的公民，引导学生从出行、购物、用水、家电和餐具使用方面反省自己的生活方式。

请你用英文给Mike回信。

回信要点如下：1．你对低碳生活的理解2．你校展开的活动3．你最近生活方式的改变（至少选择三个方面）注意：1．词数为100左右；2．参考词汇低碳生活low carbon lifestyle 3．信的开头和结尾已为你写好（不计入你所写词数）Dear Mike,How are things going? In your last letter you talked about low carbon life. Now I’d like to share my understanding of it and my experience in the past few months.With the environment problem coming into attention, it is extremely important that we take action to protect our planet. As more people are determined to make a difference, low carbon lifestyle provides us with the perfect opportunity to do it. Interestingly, our school called on students to develop a low carbon lifestyle and become a responsible citizen several months ago. In response to the appeal, I have made some changes in my way of life, which ranges from transportation to water saving. For example, instead of asking my parents to drive me to school, I take a bus to and from school. just like my schoolmates, I now refuse to use disposable chopsticks. At home, I even persuade my parents to reuse water, even though it is not so convenient. TV and computer are important entertainment for my family, but we sometimes read instead, which, I think, may help relieve the shortage of electricity.I’m really glad to communicate with you about this topic.书面表达：（必修一Unit 2）中国女药学家屠呦呦在2015年获得了诺贝尔医学奖，中国人的骄傲。